1. Field of the Invention
The present invention relates to an angular velocity detecting apparatus used in navigation systems or posture control of an automobile and, more particularly, to an angular velocity detecting apparatus of a vibration type.
2. Related Background Art
There are conventionally known angular velocity detecting apparatuses of the vibration type utilizing the phenomenon that when a vibrating body is subjected to rotation, a new vibration according to the angular velocity of the rotation occurs due to Coriolis' force. An example of an angular velocity detecting apparatus is a rotational velocity sensor, for example, as described in the bulletin of Japanese Laid-open Patent Application No. Hei 7-55479. A vibrator used in this rotational velocity sensor has a structure that in the XY plane two excitation branches project in the direction of +Y from one side of a rectangular frame and two pickup branches project in the direction of -Y from the opposite side of the frame. In this structure, when the excitation branches are excited to vibrate in the X-directions, the excitation branches also vibrate in the Z-directions because of the Coriolis' force occurring with rotation of the vibrator. This vibration in the Z-directions (in the directions normal to the XY plane) is transmitted to the pickup branches. In the pickup branch side, this Z-directional vibration thus transmitted is detected and the angular velocity of rotation of the vibrator is derived from a detection result.
This prior art vibrator has a mounting base inside the frame and the mounting base is linked with the frame by cross bridges disposed between the mounting base and either side of the frame on which the excitation branches or the pickup branches are provided. This vibrator is fixed to a body to be detected by mounting the mounting base to a stator fixed to the body to be detected. When parts of the vibrating bars are fixed, vibration of the vibrating bars is decreased. This is because the vibration propagates to the stator, and this propagation of vibration is called leakage of vibration. The higher the fixing strength between the vibrating bars and the stator, the greater the leakage of vibration. However, the above prior art rotational velocity sensor gives flexibility to the fixing strength by the above-stated structure of the vibrator, thereby preventing energy of the Z-directional vibration of the vibrating bars from leaking through the frame to the stator. Thus suppressed is degradation of detection accuracy due to the leakage of vibration.